Plant Cell Reports最新文献

Key message: Rice CC-BED NLR Xa1 recognizes TAL effectors through the interaction between ERF101 and TAL effectors. The rice Xa1 gene encodes a nucleotide-binding leucine-rich repeat receptor with an N-terminal coiled coil-zinc finger BED (CC-BED) domain. Xa1 recognizes the transcription activator-like (TAL) effectors of Xanthomonas oryzae pv. oryzae (Xoo) in the nucleus, triggering a number of immune responses, including hypersensitive cell death. We previously discovered that the rice transcription factor ERF101 directly interacts with Xa1, and functions as a positive regulator of Xa1-dependent immunity. However, the involvement of ERF101 in Xa1-induced immunity remains unclear. We herein demonstrated that the expression of the CC-BED domain in rice protoplasts inhibited Xa1-induced cell death. However, the CC-BED^C165A,C168A domain which has mutations of cysteine residues conserved in the zinc-finger motifs of BED domains and is essential for forming tetrahedral coordination geometry, failed to inhibit cell death or interact with ERF101. Therefore, Xa1-induced cell death appears to depend on the interaction between the BED domain and ERF101. In addition, we generated transgenic plants overexpressing N-terminal or C-terminal FLAG-tagged ERF101. FLAG-ERF101 transgenic plants exhibited reduced levels of Xa1-mediated immunity against Xoo, even though the overexpression of ERF101-FLAG or non-tagged ERF101 enhanced immunity. This result was consistent with the CC-BED domain interacting with C-terminal tagged ERF101, but not N-terminal tagged ERF101, whereas N-terminal and C-terminal tagged ERF101 both interacted with TAL effectors. Therefore, the interaction between the BED domain and ERF101 appears to be essential for the recognition of TAL effectors by Xa1.

Key message: OsUGT72F1 enhances heat tolerance in plants by improving ROS scavenging and modifying multiple metabolic pathways, under the regulation of transcription factors OsHSFA3 and OsHSFA4a. High temperature is one of the most critical environmental constraints affecting plant growth and development, ultimately leading to yield losses in crops such as rice (Oryza sativa L.). UDP (uridine diphosphate)-dependent glycosyltransferases (UGTs) are believed to play crucial roles in coping with environmental stresses. However, the functions for the vast majority of UGTs under high temperature stress remain largely unknown. In this study, we isolated and characterized a high temperature responsive UDP-glycosyltransferase gene OsUGT72F1 in rice. Our findings demonstrated that overexpression of OsUGT72F1 enhanced heat-stress tolerance, while the mutant plants displayed a sensitive phenotype under the same stress conditions. Ectopic expression of OsUGT72F1 in Arabidopsis thaliana also conferred improved heat tolerance to the plants. Further investigation revealed that OsUGT72F1 reduced the generation of reactive oxygen species (ROS) and boosted the activity of antioxidant enzymes, thereby alleviating oxidative damage under heat-stress conditions. Moreover, transcriptomic analysis indicated that the action of OsUGT72F1 leads to the upregulation of multiple metabolic pathways including phenylpropanoid biosynthesis, zeatin biosynthesis, and flavonoid biosynthesis. In addition, the upstream regulatory mechanism of the OsUGT72F1 gene has been identified. We found that the transcription factors OsHSFA3 and OsHSFA4a can bind to the OsUGT72F1 promoter and enhance its transcription level. Together, this study revealed that the glycosyltransferase gene OsUGT72F1 plays a vital role in the adaptive adjustment of high temperature stress in plants, revealing a new heat tolerance pathway and providing a promising gene candidate for the breeding of heat-resistant crop varieties.

Key message: GhPMEI58 is a functional pectin methylesterase inhibitor, negatively regulates ray petal elongation by inhibiting cell expansion. Petal size plays a crucial role in the quality of ornamental flowers, which is largely determined by cell expansion. However, the molecular mechanisms controlling this trait are still unknown. In this study, we reported GhPMEI58 (pectin methylesterase inhibitor 58), a functional pectin methylesterase inhibitor, negatively regulates ray petal elongation by inhibiting cell expansion. The expression of GhPMEI58 was found to be highest in ray florets and increased with ray petal elongation. Subcellular localization analysis showed that the GhPMEI58 protein is localized on the cell membrane. By stably overexpressing GhPMEI58 in Arabidopsis, we detected a decrease in pectin methylesterase activity in roots and flowers, and an increase in the degree of pectin methylation, indicating that GhPMEI58 functions as a pectin methylesterase inhibitor. Further transient overexpression and virus-induced gene silencing experiments in gerbera ray florets confirmed that GhPMEI58 is a negative regulator of ray petal elongation. Additionally, the activity assay of pectin methylesterase showed it has a trend of first rising and then falling during ray floret development. This study explores the regulatory mechanism of ray petal elongation in gerbera from the perspective of cell wall methylesterification modification, providing valuable information for improving gerbera varieties and breeding superior cultivars.

Key message: Twenty-nine GRAS genes were identified in passion fruit, the N-terminal regions and 3D (three-dimensional) structures were closely related with their tissue-specific expression patterns. Candidate PeGRASs for enhancing stress resistance were identified. Passion fruit (Passiflora edulis Sims) is a tropical fruit crop with significant edible and ornamental value, but its growth and development are highly sensitive to environmental conditions. The plant-specific GRAS gene family plays critical roles in regulating growth, development, and stress responses. Here, we performed the first comprehensive analysis of the GRAS gene family in passion fruit. A total of 29 GRAS genes were identified and named PeGRAS1 to PeGRAS29 based on their chromosomal locations. Phylogenetic analysis using GRAS proteins from passion fruit, Arabidopsis, and rice revealed that PeGRAS proteins could be classified into 10 subfamilies. Compared to Arabidopsis, passion fruit lacked members from the LAS subfamily but gained one GRAS member (PeGRAS9) clustered with the rice-specific Os4 subfamily. Structural analysis performed in silico revealed that most PeGRAS members were intron less and exhibited conserved motif patterns near the C-terminus, while the N-terminal regions varied in sequence length and composition. Members within certain subfamilies including DLT, PAT1, and LISCL with similar unstructured N-terminal regions and 3D structures, exhibited similar tissue-specific expression patterns. While PeGRAS members with difference in these structural features, even within the same subfamily (e.g., DELLA), displayed distinct expression patterns. These findings highlighted that the N-terminal regions of GRAS proteins may be critical for their specific functions. Moreover, many PeGRAS members, particularly those from the PAT1 subfamily, were widely involved in stress responses, with PeGRAS19 and PeGRAS26 likely playing roles in cold tolerance, and PeGRAS25 and PeGRAS28 in drought resistance. This study provides a foundation for further functional research on PeGRASs and offers potential candidates for molecular breeding aimed at enhancing stress tolerance in passion fruit.

Key message: Foliar-applied Zn on Catharanthus roseus enhanced production of vindoline, the main impediment precursor for costly anticancer bisindoles. A leaf-abundant CrZIP was characterized for likely role in modulating vindoline metabolism. The leaf-localized Catharanthus roseus alkaloid, vindoline, is the major impediment precursor in the production of scanty and expensive anticancer bisindoles, vinblastine and vincristine. Earlier studies have hinted toward the role of micronutrients in its accumulation. Here, the effect of various micronutrients on the leaf vindoline content was analyzed. Foliar application of zinc (Zn, 100 ppm) was found to be most effective for enhancing the vindoline content. Comparison of leaf samples of Zn-treated and control plants was performed using paired-end transcriptome sequencing and promising candidates among the differentially expressed genes were identified. A zinc-regulated, iron-regulated transporter-like proteins (ZIP) family member, which was found to be upregulated in Zn-treated samples, was taken up for functional characterization. Complementation of the zrt1/zrt2 yeast mutant (ZHY3) by CrZIP suggested that it encodes a functional Zn transporter. VIGS and transient overexpression of CrZIP in C. roseus showed a direct relationship between its expression and vindoline content. GFP fusion-based subcellular localization indicated chloroplast localization of CrZIP. Previously, vindoline biosynthesis has been reported to be dependent on intact chloroplasts. The chloroplast localization of CrZIP and its direct relationship with vindoline content in this study identifies the possible role of CrZIP, in modulating zinc-induced vindoline accumulation in the plant.

Key message: A high-throughput sequencing identified 1283 lncRNAs in anthers at different stages in Arabidopsis and their relationship with protein-coding genes and miRNAs during anther and pollen development were analyzed. Long non-coding RNAs (lncRNAs) are important regulatory molecules involved in various biological processes. However, their roles in male reproductive development and interactions with miRNAs remained elusive. In this study, a high-throughput sequencing of anthers at different developmental stages in Arabidopsis identified 1283 lncRNAs including 524 differentially expressed lncRNAs (DELs). Most of these DELs exhibited positive correlations with the expression patterns of adjacent protein-coding genes. Weighted gene co-expression network analysis (WGCNA) revealed that protein-coding genes targeted by DELs in four modules related to the tetrad stage were associated with functions such as pollen wall formation, pollen germination, or pollen tube growth, respectively. Furthermore, five, 10, and 11 lncRNAs were predicted as miRNAs' endogenous target mimics (eTMs), precursors, and natural antisense transcripts of pri-miRNA, respectively. Remarkably, the lncRNA, host gene of ath-miR167a (ath-miR167aHG), predicted as the precursor of miR167a, was selected for function validation. Its overexpression resulted in the up-regulation of miR167a and the subsequent down-regulation of miR167a's target genes ARF6 and ARF8, demonstrating a functional interaction between ath-miR167aHG and miR167a. The transgenic plants showed delayed flowering, shorter filaments, abnormal anther dehiscence, and undeveloped siliques ultimately, suggesting a role of ath-miR167aHG in male reproductive development. Collectively, our research shed new light on the functions of lncRNAs in male reproductive development and uncovered the unique interactions between lncRNAs and miRNAs.

Key message: GeCXE9 can catalyze the hydrolysis of parishin A via two pathways during the medicinal processing of Gastrodia elata. Gastrodia elata Bl. is used in traditional Chinese medicine for its bioactive compounds, particularly phenols. The molecular mechanisms of phenols formation and regulation remain to be fully explored. Here, we identified 13 GeCXE genes in G. elata. These members were mapped to eight chromosomes and possessed motifs necessary for catalysis. Phylogenetic analyses grouped them into four categories, supported by gene structure and motif composition. The cis-acting elements analysis indicated most GeCXEs contained elements associated with plant hormones or stress response. In vitro expression experiments revealed that GeCXE9 can catalyze the hydrolysis of parishin A via two pathways, producing parishin B and parishin C, respectively. Whereas in the absence of GeCXE9, parishin A is hydrolyzed solely to parishin B. In conclusion, GeCXE9 plays a crucial role in determining the metabolic pathways of phenols in G. elata, and its discovery provides a viable approach for the artificial regulation of phenols in this species.

Key message: RrUNE12 binds to the RrGGP2 promoter to facilitate biosynthesis of AsA in Rosa roxburghii fruit. Furthermore, RrUNE12 upregulates antioxidant-related genes and maintains ROS homeostasis, thereby improving tolerance to salt stress. L-ascorbic acid (AsA) plays an essential role in stress defense as a major antioxidant in plant cells. GDP-L-galactose pyrophosphatase 2 (RrGGP2) has been previously identified as the key structural gene operating in AsA overproduction in Rosa roxburghii fruit. However, the transcriptional regulation of RrGGP2 in response to abiotic stress is not fully elucidated. In this study, we identified a bHLH transcription factor, RrUNE12, whose transcription level significantly correlated with RrGGP2 abundance and AsA accumulation in developing fruit. RrUNE12 is localized in the nucleus and specifically binds to the promoter of RrGGP2 to promote its transcription. The overexpression or silencing of RrUNE12 in R. roxburghii fruit and fruit callus further confirmed that RrUNE12 positively regulated RrGGP2 transcription and AsA level. Different abiotic stress treatments indicated that RrUNE12 was greatly induced by salt. Exogenous NaCl treatment on the RrUNE12-overexpressing or RrUNE12-silencing fruits also led to enhanced transcripts abundance of both RrUNE12 and RrGGP2, compared to the treatment without adding NaCl. RrUNE12 overexpression in fruit callus alleviated salt stress damage by upregulating the expression of RrGGP2 and antioxidant-related genes. Additionally, stable overexpression of RrUNE12 in tomato plants resulted in a significant increase in AsA content and antioxidant capacity, accompanied by an increased resistance to the salt stress. Collectively, the results suggest that RrUNE12 functions as an activator of AsA biosynthesis in R. roxburghii fruit and plays a positive role in mitigating salt stress by increasing both AsA level and the oxidation resistance.

Key message: We generated soybean mutants related to two ß-amyrin synthase genes using DNA-free site-directed mutagenesis system. Our results suggested that one of the genes is predominant in the soyasaponin biosynthesis. Soyasaponins, which are triterpenoid saponins contained in soybean [Glycine max (L.) Merril], are responsible for the astringent aftertaste of soyfood, and their complete elimination from soybean seeds is a key challenge in the development of cultivars with improved taste. While the loss of function in the ß-amyrin synthase genes (GmBAS1 and GmBAS2) has proven effective in reducing soyasaponin content in soybean seeds, the specific functional roles of these genes remain unclear. In this study, site-directed mutagenesis was performed on two GmBAS loci using a DNA-free clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated endonuclease 9 (Cas9) system. A complex of sgRNA targeting sequences conserved in the two loci and Cas9 protein was introduced into the shoot apical meristems of soybean embryonic axes via bombardment. Cleaved amplified polymorphic sequences (CAPS) analysis conducted 1 month post-bombardment revealed that 138 seedlings out of 1,467 screened exhibited mutations at one or both GmBAS loci. CAPS and sequencing analysis in the subsequent generation identified a total of 16 plants with inheritable mutations ranging from one to ten nucleotides. High-performance liquid chromatography (HPLC) analysis showed that site-directed mutagenesis in the GmBAS1 locus resulted in the absence of soyasaponins in mature seeds, as well as in young roots, stems, and leaves. These findings demonstrate that GmBAS1 is the predominant ß-amyrin synthase gene in soybean plants. In addition, the DNA-free CRISPR/Cas9 system was shown to be highly efficient in inducing simultaneous mutagenesis at two target loci using a single gRNA.

Key message: Reducing endogenous CK levels accelerates fruit ripening in tomato by regulating ethylene biosynthesis and signalling pathway. Tomato is a typical climacteric fruit and is recognized as one of the most important horticultural crops globally. The ripening of tomato fruits is a complex process, highly regulated by phytohormones. Cytokinin (CK) is a hormone that primarily impacts the early development of fruit, however its influence on fruit ripening has not been thoroughly investigated. In this study, we used both wild-type Micro-Tom and transgenic tomato plants that overexpress AtCKX2, a CK degradation gene driven by the fruit-specific promoter Tfm7, to investigate the effect of CK on tomato fruit ripening. Our findings revealed that reducing endogenous CK levels in transgenic plants can accelerate the ripening process of tomato fruits. Premature activation of ethylene biosynthetic genes and ripening regulator genes was upregulated in CK-deficient fruits. Moreover, the application of exogenous ethylene inhibitors resulted in delayed fruit ripening in CK-deficient fruits. These results together suggest that CK plays a negative role in tomato fruit ripening by affecting the ethylene pathway.